morris



Feb. 14. 1956 E. o. NoRRls CENTRIFUGAL SPRAY coATING APPARATUS 7sheets-sheet 1 Filed May 14, 1952 TTORNEV Feb. 14, 1956 Filed May 14,1952 E. o. NoRRls 2,734,480

CENTRIFUGAL SPRAY COATING APPARATUS '7 Sheets-Sheet 2 INVENTOR bu/m0 O./Va/Q/Q/s ORNEY Feb.. 14, 1956 E. o. NoRRls CENTRIFUGAL SPRAY COATINGAPPARATUS 7 Sheets-Sheet 3 Filed May 14, 1952 --loRNEY Feb. 14, 1956 E.o. NoRRls CENTRIFUGAL SPRAY COATING APPARATUS 7 Sheets-Sheet 4 Filed May14. 1952 INVENTOR fau/A190 0 /l/a/ee/s ORNEY Feb. 14, 1956 E. o. NcRRls2,734,480

CENTRIFUGAL SPRAY COATING APPARATUS Filed May 14. 1952 7 Sheets-Sheet 5IIIO INVENTOR 9 7 ZW/1,90 O. /l/a/@f/s BY 1 f/ Fb. l14, 1956 E. O.NoRRls 2,734,480

CENTRIPUGAL SPRAY COATING APPARATUS Filed May 14, 1952 7 Sheets-Sheet 6vENToR 50u/4R0 /Vp/QR/S ATTCRNEY Feb. 14, 1956 2,734,480

Y El O. NORRIS CENTRIFUGAL SPRAY COATTNG APPARATUS Filed May 14, 1952 7Sheets-Sheet 7 BY l/// a' ATTORNE V United States Patent O CENTRIFUGALSPRAY COATIN G APPARATUS Edward 0. Norris, Westport, Conn..

Application May 14, 1952, Serial No. 287,799

2 Claims. (Cl. 118-326) This invention relates to apparatus forcentrifugally vspraying objects which are capable of being fed into aspray zone, and it has for an object to provide a novel and improvedapparatus for this purpose.

Another object of the invention is to provide a centrifugal sprayingapparatus having means for producing a zone of atomized spray materialcombined with a directional spray.

Another object is to provide a spraying apparatus of the type specifiedhaving means for accurately regulating the volume and consistency of theatomized spray material in accordance with the requirements of the work.to be processed.

Still another object is to provide means for maintainling a vaporpressure equilibrium in the spray zone of a centrifugal sprayer of theforegoing type so as to insure `constant material viscosity andconcentration.

Another object of the invention is to provide a centrifugal sprayingapparatus with means to maintain suit- .able solvent vapor andtemperature conditions in the atmosphere of the spray zone.

Another object is to provide means to capture and collect the sprayedmaterial which is not intercepted by the surface of the objects beingsprayed, so that this material `becomes available for respraying.

Another object is to provide a centrifugal spraying apparatus havingnovel and improved details of construction and features of operation.

Various other objects and advantages will be apparent as the nature ofthe invention is more fully disclosed.

In accordance with the present invention, the material .to be sprayed isfed to a rotating bowl which is mounted for rotation about a horizontalaxis and is driven at a speed suited to maintain a peripheral lm ofspray material due to centrifugal force. An important novel feature ofthe invention resides in the provision of an improved pick-up mechanismcomprising a rotary centrifugal feeder which dips into the rotating filmof spray material in the bowl and is driven thereby at a rate to pick Yup and discharge said material upon an adjacent rotary centrifugaldistributor which is positively driven at the optimum speed to dischargethe material as a tine spray entirely within the confines of theenclosure. This fine spray strikes and settles upon the Work pieceswhich pass through the bowl on a suitable conveyor. These rotaryfeeder-distributor units can be installed in various locations and atvarying angles throughout the bowl to attain the desired coverage ofirregularly shaped work.

. A solvent vapor pressure equilibrium which ensures a constant materialviscosity is maintained within the bowl by `a novel`construction ofinlet and outlet chambers and associated elements. l

, Other important novel features, hereinafter more fully described,include means for feeding spray material onto the rotating film in thebowl in such a way that the incoming material is assimilated into the lmwithout turbulence; means for controlling the thickness of the rotating,film of spray material" by continuously removing and discharging excessmaterial from the machine; means for adjusting the feeder-distributorunit or units to control the volume and consistency of the spray meansfor controlling the operating temperatures at various stages oftreatment either by heating or cooling according to individualrequirements; means for collecting oversprayed material; and variousrefinements in structural details and Fig. 1 is a longitudinal verticalsection taken online- 1 1 of Fig. '2 through a spraying device embodyingthe present invention;

Fig. 2 is a transverse vertical section taken on line 2 2 of Fig. 1;

Fig. 3 is a transverse vertical section taken on line 3 3 of Fig. l

Fig. 4 is a longitudinal section, on an enlarged scale,`

through the rotary distributor and feeder;

Fig. 5 is a transverse section taken on line 5 5 of Fig. 4;

Fig. 6 is a vertical section on line 6 6 of Fig. 1,show

ing a detail of the adjustable drive for the rotary bowl;

Fig. 7 is a fragmentary vertical section, on an enlarged scale, showingthe means for adjusting the position of the rotary feeder;

Fig. 8 is a section taken on line 8 8 of Fig. 7;

Fig. 9 is a longitudinal vertical section villustrating a modificationof the rotary distributor of Fig. 4;

Fig. 10 is a transverse vertical section through the endless conveyor ofFig. 1, showing how articles to be coated (in this instance a dish) areconveyed through the spraying device;

Fig. 1l is a longitudinal vertical section through the drain containingthe overflow disc assembly for'controlling the thickness of the film ofspraying material in the rotary bowl of Fig. 1;

Fig. l2 is a transverse section taken on line 12-12 of Fig. 1l;

Fig. 13 is a transverse vertical section on line 13 13 of Fig. l,showing details of the vapor-sealing housing;

Fig. 14 (on Sheet 3) is a fragmentary transverse vertical sectionthrough the rotary bowl, diagrammatically illustrating the pick-olf andspraying action of the rotary distributor and feeder assembly;

Fig. 15 is a sectional view similar to Fig. 4 illustrating an embodimentusing a stationary pick-up;

Fig. 16 is a transverse section taken on the line 16 16 of Fig. 15; andv Fig. 17 is a broken perspective view of the pick-olf member of Figs.l5 and 16.

In the following description certain specific terms are used forconvenience in referring to the various details of the invention. Theseterms, however, are to be interpreted as broadly as the state of the artwill permit.

The centrifugal spraying machine shown in Fig. l comprises a rotatablecentrifugal bowl `or casing 1 which in this embodiment is made of twoidentical angular bellshaped halves having mating peripheral flanges 2secured together as by bolts 3.

The bowl 1 is rotatably supported on a plurality ofv rollers or wheels,for example by thre rubber-tired wheels 4 supporting each annular endhub of the bowl as shown in Figs. l, 2 and 3. These wheels 4 arejournaled in bearing bushings 5 mounted in end `plates 6 which are;

Patented Feb. 14, 1956 secured to the base 7 and are secured together bylongitudinal rods 8.

One of the wheels 4 (that shown at the lower left of Fig. 1) ispositively driven by motor 9 through belt 1) driving pulley 12 on shaft13 which carries said wheel 4; all of the other tive wheels beingidlers. The shaft 13 is journaled in a bearing 14 mounted eccentricallyin a sleeve 15 as shown in Fig. 6; and said sleeve 15 is se cured by setscrew 16 to the bushing 5 on the said end plate 6 of the machine. Uponloosening the set screw 16 and rotating sleeve 15 in bushing 5, theeccentric mounting of the bearing 14 in sleeve 15 enables the drivenwheel 4 to be adjusted with respect to the adjacent end hub of bowl 1 soas to compensate for wear on the rubber tire of said wheel 4. The idlerwheels may be similarly mounted for adjustment.

The sides, bottom and top of the machine are enclosed by a wall orcasing 17 secured to the end plates 6, as shown in Figs. l and 3. In theembodiment illustrated, the casing 17 has an enlarged central hood 18disposed about the central portion of the rotatable bowl 1 andcontaining a series of heating lamps 19 which register with spacedopenings 20 formed in a partition 21 in said hood for the purpose ofheating the bowl 1 when the sprayable material requires heat in order tomaintain a desired consistency during the spraying operation.

The annular ends of bowl 1 are aligned with circular openings 23 in theend plates 6 of the machine and stationary members forming inlet andoutlet chambers 24 and 25 are secured to the respective end plates 6 inregistry with said openings 23. A horizontal conveyor 26, for carryingthe objects to be sprayed, extends longitudinally through inlet chamber24, rotary bowl 1, and outlet chamber 25.

In the embodiment illustrated, conveyor 26 comprises a pair of spacedstationary hollow tracks or channels 27 which are enclosed except fornarrow longitudinal slots or openings 2S which extend the full length ofeach channel along the lower outer edge thereof, as shown in Fig. l0.Endless link chains 29 track in the channels 27., and various links(such as alternate links) of one chain 29 are joined to correspondinglinks of the other chain 29 by wire rods 30 which are appropriately bentor formed to extend through the openings 28 in channels 27. and formnarrow transverse seats for supporting the articles to be sprayed, suchas thel dish 31- shown in Fig. l0. During the operation of the machinethe endless conveyor is moved continuously by any suitable actuatingmeans (not shown) the movement through the machine being from left toright in Fig. l. The location and restricted size of the longitudinalopenings 28 inV channels 27 minimizes the ingress of spray material tosaid channels.

' The inlet and outlet chambers 24 and 25 are constructed to insure aneffective vapor seal between said chambers and the rotary bowl 1 wherethe spraying takes place, the purpose of such seal being to minimize thewaste of spray material and maintain a substantially constant vaporconsistency. In the embodiment illustrated, chambers 24 and 25 areidentical except that inlet chamber 24 has inlet openings which areclosed by swinging doors or flaps, while outlet chamber 25 has permanentoutlet openings which are restricted according to the size and shape ofthe objects to be sprayed. Accordingly, corresponding parts of chambers24 and 25 are identiied by the same reference numerals in Figs. l, 2, 3and 13. Of course, either or both of the chambers may have fixed wallsor either or both may have swinging aps as desired.

Inlet and Outlet chambers 24 and 25 each have an outer wall 34, an innerwall 35 secured to the adjacent end plate 6 as by screws 36, and hollowjacketed angular top and curved bottom walls 37 and 38, as shown inFigs. 1 and 13. The outer and inner walls 34 and 35 of both chambers 24and 25 have spaced rectangular openings 39 in which the stationaryhollow channels 27 of 4 conveyor 26 are seated and secured, as shown inFigs. 1, 2, 3 and 13.

In the case of inlet chamber 24, the portion of each outer and innerwall 34 and 35 above the openings 39 has a truncated-triangular-shapedopening 49 which is substantially closed by a similarly shaped swingingdoor or ap 41 hinged to such wall at 42, as shown in Figs. l and 3. Thehinged tlaps 41 of inlet chamber 24 swing inwardly as indicated by thedotted lines in Fig. l; hence, as the endless conveyor 26 advances fromleft to right in Fig. l, conveying the articles to be sprayed (such asdishes 31 of Fig. l0) the pressure of the advancing articles on aps 41will swing said flaps about their hinges 42 suiciently to pass saidarticles, after which the flaps will immediately return to the closedposition shown in full lines in Fig. l. The lower inner edge of eachhinged ap 41 is shaped to form an upturned open channel or lip 43 whichslopes downwardly from its central obtuse-angled apex as shown in Figs.1 and 3 for the purpose of collecting condensed spray material andallowing it to low onto the downwardly sloping walls of chamber 24 andbowl 1.

In the case of outlet chamber 25, the portion of each outer and innerwall 34 and 35 above the openings 39 has an opening 45 of any suitableshape and size, but preferably only large enough to conveniently passthe articles treated by the spraying machine. For example, in the caseof a machine for spraying articles such as the dish 31 of Fig. l0, theelongated low opening 45 of Figs. 2 and 13 is satisfactory, The upperinterior edge of said opening 4S is shaped to form an upturned openchannel or lip 46 which slopes downwardly from its central obtuseangledapex as shown in Figs. l and 2, for the purpose of collecting spraymaterial and allowing it to ow onto the downwardly sloping walls ofchamber 25 and bowl 1 instead of dripping onto the article beingprocessed.

The hollow top and bottom walls 37 and 38 of inlet and outlet chambers24 and 25 (Figs. l and 13) may be supplied with a heating or coolingmedium from any suitable supply source (not shown) depending upon thepurpose for which the machine is used. For example, in some cases it maybe desirable to circulate hot water through one or bothl of thesejacketed walls to assist in controlling the treating temperature. Inother cases it may be advantageous to circulate a cooling uid throughone or both of said walls to accelerate the condensation of the spraysolvent and prevent the-escape thereof. The cooling, however, should becontrolled to prevent condensation of atmospheric moisture. The angulartop walls 37 of said inlet and outlet chambers 24 and 25 are soconstructed (at a suitable angle, preferably in excess of 45, such asillustrated in Figs. Zand 13) in order that spray material collecting onthese interior sloping walls will flow down said walls into the curvedbottom wall, and not drop down vertically and spatter on the objectscarried by the conveyor 26.

A pan is shown as disposed beneath the conveyor 26 in a position tocollect the oversprayed material that is not intercepted by the workpiece or direct spray in the event that no workpiece is present. The pan110 drains through a duct 111 which leads to a receiver, not shown. Thepan may be secured to the walls 35 and the duct 111 may extend outwardlythrough the walls 34 and 35 of the outlet chamber 25. The purpose of thepan 110 is to remove over-sprayed material from the spray zone so thatthe viscosity of the spray material in the annulus is not built up byloss of solvent. The vco1- lected material can of course be re-fed tothe bowl after its viscosity has been suitably adjusted.

The rotary centrifugal bowl 1 rotates in a counterclockwise direction asviewed 'in Fig. 2. The spray material is fed into bowl 1 through a feedpipe 47 which is connected to any suitable ysource of supply (not shown)and extends through inlet chamber 24 into the bowll where the terminusof the pipe has a plurality of spaced perforations or openings 48 forfeeding the spray material onto the central cylindrical portion orannulus of the bowl. The perforated discharge end of feed pipe 47 ismounted adjacent a downwardly-moving point on the bowl (in this instanceat about the point where the numeral 7 would appear on a clock). By thusfeeding the incoming spray material under pressure onto thedownwardly-moving portion of the centrifugal film in bowl 1, theincoming spray material and the moving film have a component of movementin the same direction, with the result that the incoming material isassimilated into the film with less turbulence than would otherwise bepossible. The bowl 1 rotates about its horizontal axis at a speed suitedto maintain a peripheral film of spray material about the annulus of thebowl due to centrifugal force, as indicated in Figs. 5 and 7 where saidperipheral film is designated by the reference numeral 50.

The pick-off mechanism for picking up spray material from the startingfilm 50, and for discharging same centrifugally in a directiontransverse to the axis of bowl 1, comprises a rotary feeder 51 and arotary distributor 52 which are best shown in Figs. 1 and 4. The feeder51 is driven by the moving film 50 at a rate to discharge the spraymaterial centrifugally upon the distributor 52, while distributor 52 ispositively driven by means hereinafter described at a rate to dischargethe spray material centrifugally as a fine spray onto the articles beingadvanced through the rotary bowl. This novel combination, which will nowbe described, makes it possible to control the volume and uniformity ofdistribution of the spray with utmost precision since the feeder 51 isdriven by the lilrn 50 at a speed close to the speed of the film andthere is thus a minimum of fluid friction and turbulence, while thedistributor 52 may be driven at the most elicient speed to produce thedesired atomization.

The rotary feeder 51 and distributor 52 are both mounted on a rigid tube53 which extends into the bowl 1 and is rigidly secured outside the bowlto an arm 54 swivelled by bolt 55 on a plate 56 (Figs. 7 and 8) which inturn is secured by bolts 57 to the adjacent end plate 6 of the machine,as shown in Figs. l, 7 and 8. Adjusting bolts 58 in plate 56 extendthrough arcuate slots 59 in the arm 54 as shown in Figs. 7 and 8. Whenthese bolts are loosened if necessary, the arm 54 may be rotated on itsswivel bolt 55 to an extent determined by the length of arcuate slots59. Such rotation of arm 54 causes rotation of tube 53 which is carriedby said arm; and rotation of said tube 53 effects an adjustment in therelative positions of rotary feeder 51 and rotary distributor 52 ashereinafter described.

Referring particularly to Figs. 4 and 5, the rotary feeder 51 comprisesa tubular sleeve 61 carrying a longitudinal stack of pick-up discs 62separated by alternate spacers 63, and rotatable on ball bearings 64mounted on a shaft 65 having an enlarged end 66 rigidly secured to anarm 67 which, in turn, is secured by bolt 68 to a plate 69 welded orotherwise secured to the tube 53. The enlarged end 66 of shaft 65 isgrooved at 70 to exclude atomized spray material from the interior ofsleeve 61.

The rotary distributor 52 comprises a positively driven tubular sleeve72 carrying a longitudinal stack of distributor discs 73 separated byalternate spacers 74 and having an end plate 75 secured to said sleeve'72 by screws 76, as shown in Fig. 4. The sleeve 72 i's rotatablymounted on ball bearings 77 carried by hollow-stationary shaft 78 havingan enlarged end 79 rigidly secured to the end of tube 53. The end 79 ofshaft 78 is grooved at 80 to exclude atomized spray material from theinterior of sleeve 72. The rotary sleeve 72 carrying distributor discs73 is driven by motor 82 (Fig. l) through exible drive shaft 83 whichextends through tube 53 and hollow shaft 78 in sleeve 72 and is securedto the end plate 75 of distributor 52 by set screw 84, as shown in Fig.4. The axis of the distributor registers with the axis of the bolt 6 55so that adjustment of the arm 54 has the effect of rotating the feederabout the axis of the distributor.

A baffle 85, carried by the arm 67 is positioned to intercept materialwhich is discharged from the feeder 51 beyond the arc of the distributor52, and thus prevents such material from striking the articles on theconveyor 26. The baffle 85 is inclined to drain onto the film in thebowl 1 beyond said articles. 4

in operation, the spray material is fed into rotary bowl 1 through feedpipe 47 as previously described, and the bowl rotates continuously aboutits horizontal axis at a speed suited to maintain the peripheral film 50of spray material (Figs. 5 and 7) by centrifugal force. The discs 62 ofrotary feeder 51 dip into the rotating film 50, and, since the feeder isrotated by the lm at a speed approximating that of the film, the discs62 pick up the spray material and discharge it centrifugally upon thedistributor 52, as diagrammatically illustrated in Fig. 14. The bailleplate 85 prevents spray material from feeder 51 from passing directlyonto the articles. The distributor, being constantly driven by motor 82at the most eicient speed to produce the desired atomization, dischargesthe spray material centrifugally as a directional spray and as a linemist throughout the enclosed area.

Before the machine is set in operation the desired setting of rotaryfeeder 51 with respect to rotary distributor 52 is effected by looseningbolt 68 (Figs. 4 and 5) and suitably tilting the arm 67 (which carriesfeeder 51) upon plate 69, after which bolt 68 is tightened. However,when it is desired to adjust feeder 51 while the machine is inoperation, in order to move the pick-up discs 62 toward or away from theperiphery of bowl 1 and thereby vary the extent to which said discs 62dip into the rotating film 58 of spray material, this is accomplished inthe manner illustrated in Figs. 7 and 8. Upon loosening bolts 55 and 53,if necessary, and rotating the arm S4 which carries tube 53, theresulting rotation of said tube 53 rotates plate 69 and arm 67 carryingrotary feeder 51. The rotary feeder is thus rotated slightly about theaxis of the distributor 52, as indicated by the broken lines in Fig. 7,causing the feeder to be adjusted toward or away from the innerperiphery of bowl 1 and thus varying the amount of spray material pickedup by discs 62 of the feeder.

A drain or discharge device for controlling the thickness of the lilm ofspray material 50 is illustrated in Figs. l, 2, ll and 12. Thiscomprises a rotary drum 87 carrying a stack of spaced discs S8 androtatably mounted in a drain pan 89 rigidly supported by a drain pipe96) extending into the inlet chamber 24 and connected to any suitablecollecting receptacle, not shown. The drain device is located at anysuitable point in bowl 1, for example at a downwardly-moving point onthe bowl between the rotary feeder-distributor assembly and the feedpipe 47, as shown in Fig. 2. The drain device is mounted so that thediscs 88 are spaced a predetermined distance from the cylindricalsurface or annulus of bowl 1, according to the desired thickness of thespray material, and, when the rotating film 50 of spray material exceedsthe desired depth or thickness, the discs 88 dipping into the film pickup the excess spray material and discharge it centrifugally into drainpan 89 from which itis discharged through drain pipe 90.

The modified rotary distributor illustrated in Fig. 9 is similar to thatpreviously described except that it is actuated by a compressed airmotor 92, the drive shaft 93 of which is keyed to the end plate oftubular sleeve 72 by set screw 84. Motor 92 has an air inlet tube 94 andan air Vent tube 95, the inlet tube serving to support the distributorwithin the rotary bowl 1 in the manner previously described inconnection with the rigid tube 53 of Fig. 4. The motor has a stationarycollar 96 which is spirally grooved at 97 in a direction to excludespray material from the motor assembly, and the end plate 98 supports aplate or bracket 99 which is secured thereto 7 by bolt 100-and(liketheplate 69 of Fig. 4) carries the rotary feeder 51 which isomitted-from Fig.- 9 in order to simplify the showing. The other partsof the distributor of Fig. 9 are similar to the corresponding parts ofthe distributor 52 of Fig. 4 and are identied by similar referencenumerals for purposes of comparison.

Figs. 15-17 illustrate a further embodiment of the invention in whichthe rotary feeder of Figs. 1-15 is replaced by a stationary feeder 115in the form of a comb comprising a base member 116 mounted on a bar 117which is secured in a bracket 113 which is attached to the tube 53similarly to the arm 69 of Fig. 4. The angular position of the comb canbe adjusted by releasing set screw 119. The base member 116 is formedwith channels 120 in which teeth 121 are mounted and are secured bysuitable means as by welding. The teeth 121 have points 122 which dipinto the advancing peripheral film of material in the bowl 1 and detiecta spray of such material onto the distributor 52 which is similar to thedistributor 52 of Fig. 4. The teeth 121 are made of a hard metal suitedto withstand the abrading action of the spray material. The teeth 121serve also as mixing means to agitato and mix the material in the bowl 1and thus prevent stratification due to centrifugal separation. ln somecases it has been found advisable to utilize both a rake for mixing anda rotary feeder for feeding the distribution.

The distributor 52, in the various embodiments shown, may be disposed atan angle to the axis of the bowl if desired to effect the proper spraypattern in accordance with the work being processed.

Although certain specific embodiments of the invention have been shownfor purposes of illustration, it is to be understood that the inventionis capable of various uses and that changes and adaptations may be madetherein as will be readily apparent to a person skilled in the art. Theinvention is only to be restricted in accordance with the scope of thefollowing claims.

What is claimed is:

l. A spraying apparatus comprising a bowl mounted to rotate, said bowlhaving an opening in at least one end and having an inner surfaceforming an annulus to retain a spray-forming material, means forrotating said bowl to cause said material to form centrifugally aperipheral film in said bowl, means including xed top walls mountedoutside of said bowlend `fom.

ing a chamber communicatingthroughf said `opn exid with the the interiorVoffsaid bowl, meansto convey` articles to be sprayed into and out ofsaid bowl through said chamber, said top walls sloping at an angle of atleast 45 degrees and having their'entir'e lower edges disposed beyondthe path of said larticles to cause collected yspray material to flowalong the lunder surface of said walls away from the articles beingsprayed, a sprayer positioned to projectv spray-forming material as aspray to form a spray zone within said bowl adapted to spray articleswhile in said zone.

2. A spraying apparatus comprising a bowl mounted to rotate, said bowlhaving an opening in at least one end and having an inner surfaceforming an annulus to retain a spray-forming material, means forrotating said bowl to cause said material to form centrifugally :frperipheral tilm in said bowl, means including fixed top walls mountedoutside of said bowl 'end forming a. chamber communicating through saidopen end with the interior of said bowl, means to convey articles to'besprayed into and out of'said bowl through said chamber, all stationarysurfaces above the path of said articles including said top Wallssloping at an angle of atleast 45 degrees and having their entire loweredges disposed beyond the path of said articles to cause collected spraymaterial to flow along the under surface of said walls away from thearticles being sprayed, a, sprayer positioned to project spray-formingmaterial as a spray to form a spray zone within said bowl adapted tospray articles while in said zone.

References Cited in the ile of this patent UNITED STATES PATENTS1,964,790 Roberts July 3, 1934 2,553,408 Foster May 15, 1941 2,261,988Gaebel Nov. 11, 1941 2,375,434 Moise et al. May 8, 1945 2,454,594Christensen Nov. 23, 1948 2,528,087 Schoepe Oct. 31, 1950 2,587,514Norris Feb. 26, 1952 2,597,021 Norris May 20, 1952 FOREIGN PATENTS24,254 Great Britain Oct. 19, 1911

